Detection of clonal plasma cells in POEMS syndrome using multiparameter flow cytometry.

POEMS syndrome (polyneuropathy, organomegaly, endocrinopathy, monoclonal protein [M-protein], and skin changes) is a rare systemic disorder characterized by various symptoms caused by underlying plasma cell (PC) dyscrasia. Detection of monoclonal PCs is mandatory for the diagnosis of POEMS syndrome; however, the usefulness of EuroFlow-based next-generation flow cytometry (EuroFlow-NGF) in POEMS syndrome for detecting monoclonal PCs in bone marrow (BM) and the gating strategy suitable for flow cytometry study of POEMS syndrome remain unknown. We employed EuroFlow-NGF-based single-tube eight-color multiparameter flow cytometry (MM-flow) and established a new gating strategy (POEMS-flow) to detect the monoclonal PCs in POEMS syndrome, gating CD38 broadly from dim to bright and CD45 narrowly from negative to dim compared to MM-flow. MM-flow detected monoclonal PCs in 9/25 (36.0%) cases, including 2/2 immunofixation electrophoresis (IFE)-negative cases (100%). However, POEMS-flow detected monoclonal PCs in 18/25 cases (72.0%), including 2/2 IFE-negative cases (100%). POEMS-flow detected monoclonal PCs with immunophenotypes of CD19- in 17/18 (94.4%). In six cases where post-treatment samples were available, the size of the clones was significantly reduced after the treatment (P = 0.031). POEMS-flow can enhance the identification rate of monoclonal PCs in POEMS syndrome and become a valuable tool for the diagnosis of POEMS syndrome.

[Identification of transcriptional features and surface markers of plasma cell clones in POEMS syndrome by single-cell RNA sequencing].

POEMS syndrome is a rare monoclonal plasma cell disorder with unique symptoms distinct from other plasma cell neoplasms. To identify and find the transcriptional features of clonal plasma cells in POEMS syndrome (POEMS clones), single-cell RNA sequencing was performed on patient-derived bone marrow plasma cells. POEMS clones were identified in 5 out of 10 patients, and the proportions of POEMS clones in the plasma cells were markedly smaller than that of other plasma cell malignancies such as multiple myeloma and MGUS. The transcriptional features of POEMS clones differed from those of other plasma cell diseases, and representative MM-related oncogenes were not upregulated in POEMS clones. Notably, POEMS clones are negative for CD19 and express significantly lower MHC-II levels than normal plasma cells; thus, CD19- HLA-DRlo is confirmed as a useful marker to identify POEMS clones in patients. These findings unveil the unique features of POEMS clones and contribute to the understanding of the pathogenesis of POEMS syndrome.

Polycomb repressive complex 1.1 coordinates homeostatic and emergency myelopoiesis.

Polycomb repressive complex (PRC) 1 regulates stem cell fate by mediating mono-ubiquitination of histone H2A at lysine 119. While canonical PRC1 is critical for hematopoietic stem and progenitor cell (HSPC) maintenance, the role of non-canonical PRC1 in hematopoiesis remains elusive. PRC1.1, a non-canonical PRC1, consists of PCGF1, RING1B, KDM2B, and BCOR. We recently showed that PRC1.1 insufficiency induced by the loss of PCGF1 or BCOR causes myeloid-biased hematopoiesis and promotes transformation of hematopoietic cells in mice. Here we show that PRC1.1 serves as an epigenetic switch that coordinates homeostatic and emergency hematopoiesis. PRC1.1 maintains balanced output of steady-state hematopoiesis by restricting C/EBPα-dependent precocious myeloid differentiation of HSPCs and the HOXA9- and ß-catenin-driven self-renewing network in myeloid progenitors. Upon regeneration, PRC1.1 is transiently inhibited to facilitate formation of granulocyte-macrophage progenitor (GMP) clusters, thereby promoting emergency myelopoiesis. Moreover, constitutive inactivation of PRC1.1 results in unchecked expansion of GMPs and eventual transformation. Collectively, our results define PRC1.1 as a novel critical regulator of emergency myelopoiesis, dysregulation of which leads to myeloid transformation.

The pathogenetic significance of exhausted T cells in a mouse model of mature B cell neoplasms.

Dysfunctional anti-tumor immunity has been implicated in the pathogenesis of mature B cell neoplasms, such as multiple myeloma and B cell lymphoma; however, the impact of exhausted T cells on disease development remains unclear. Therefore, the present study investigated the features and pathogenetic significance of exhausted T cells using a mouse model of de novo mature B cell neoplasms, which is likely to show immune escape similar to human patients. The results revealed a significant increase in PD-1+ Tim-3- and PD-1+ Tim-3+ T cells in sick mice. Furthermore, PD-1+ Tim-3+ T cells exhibited direct cytotoxicity with a short lifespan, showing transcriptional similarities to terminally exhausted T cells. On the other hand, PD-1+ Tim-3- T cells not only exhibited immunological responsiveness but also retained stem-like transcriptional features, suggesting that they play a role in the long-term maintenance of anti-tumor immunity. In PD-1+ Tim-3- and PD-1+ Tim-3+ T cells, the transcription factors Tox and Nr4a2, which reportedly contribute to the progression of T cell exhaustion, were up-regulated in vivo. These transcription factors were down-regulated by IMiDs in our in vitro T cell exhaustion analyses. The prevention of excessive T cell exhaustion may maintain effective anti-tumor immunity to cure mature B cell neoplasms.

An Aged/Autoimmune B-cell Program Defines the Early Transformation of Extranodal Lymphomas.

A third of patients with diffuse large B-cell lymphoma (DLBCL) present with extranodal dissemination, which is associated with inferior clinical outcomes. MYD88L265P is a hallmark extranodal DLBCL mutation that supports lymphoma proliferation. Yet extranodal lymphomagenesis and the role of MYD88L265P in transformation remain mostly unknown. Here, we show that B cells expressing Myd88L252P (MYD88L265P murine equivalent) activate, proliferate, and differentiate with minimal T-cell costimulation. Additionally, Myd88L252P skewed B cells toward memory fate. Unexpectedly, the transcriptional and phenotypic profiles of B cells expressing Myd88L252P, or other extranodal lymphoma founder mutations, resembled those of CD11c+T-BET+ aged/autoimmune memory B cells (AiBC). AiBC-like cells progressively accumulated in animals prone to develop lymphomas, and ablation of T-BET, the AiBC master regulator, stripped mouse and human mutant B cells of their competitive fitness. By identifying a phenotypically defined prospective lymphoma precursor population and its dependencies, our findings pave the way for the early detection of premalignant states and targeted prophylactic interventions in high-risk patients. SIGNIFICANCE: Extranodal lymphomas feature a very poor prognosis. The identification of phenotypically distinguishable prospective precursor cells represents a milestone in the pursuit of earlier diagnosis, patient stratification, and prophylactic interventions. Conceptually, we found that extranodal lymphomas and autoimmune disorders harness overlapping pathogenic trajectories, suggesting these B-cell disorders develop and evolve within a spectrum. See related commentary by Leveille et al. (Blood Cancer Discov 2023;4:8-11). This article is highlighted in the In This Issue feature, p. 1.

Unraveling unique features of plasma cell clones in POEMS syndrome with single-cell analysis.

POEMS syndrome is a rare monoclonal plasma cell disorder, with unique symptoms distinct from those of other plasma cell neoplasms, including high serum VEGF levels. Because the prospective isolation of POEMS clones has not yet been successful, their real nature remains unclear. Herein, we performed single-cell RNA-Seq of BM plasma cells from patients with POEMS syndrome and identified POEMS clones that had Ig λ light chain (IGL) sequences (IGLV1-36, -40, -44, and -47) with amino acid changes specific to POEMS syndrome. The proportions of POEMS clones in plasma cells were markedly smaller than in patients with multiple myeloma (MM) and patients with monoclonal gammopathy of undetermined significance (MGUS). Single-cell transcriptomes revealed that POEMS clones were CD19+, CD138+, and MHC class IIlo, which allowed for their prospective isolation. POEMS clones expressed significantly lower levels of c-MYC and CCND1 than MM clones, accounting for their small size. VEGF mRNA was not upregulated in POEMS clones, directly indicating that VEGF is not produced by POEMS clones. These results reveal unique features of POEMS clones and enhance our understanding of the pathogenesis of POEMS syndrome.

[A Case Report of Cancer Chemotherapy for Disseminated Carcinomatosis of the Bone Marrow Associated with Gastric Cancer Accompanied by Disseminated Intravascular Coagulation].

A 72-year-old woman was admitted to our hospital because of symptoms of bleeding diathesis such as hematuria and purpura. A blood test revealed disseminated intravascular coagulation(DIC). Upper gastrointestinal endoscopy showed advanced gastric cancer. Bone marrow aspiration cytology demonstrated diffuse hyperplasia of large atypical cells, and metastasis of the epithelial tumor was suspected on immunohistochemical examination. She was diagnosed with disseminated carcinomatosis of the bone marrow associated with gastric cancer accompanied by DIC. She was treated with weekly infusion of methotrexate 100 mg/m2 plus 5-fluorouracil 600 mg/m2 for 4 courses; and she completely recovered from DIC. She received oral tegafur/gimeracil/oteracil as an outpatient. However, DIC recurred 126 days after the initial chemotherapy, and 5-fluorouracil plus cisplatin was administered subsequently. After 1 course, she died 166 days after the initial chemotherapy. Although the prognosis of patients with disseminated carcinomatosis of the bone marrow associated with gastric cancer accompanied by DIC is extremely poor, this case shows that secession of DIC and prognostic improvement by chemotherapy could occur. Chemotherapy could be considered a potentially effective treatment in this case.

The combination of the tubulin binding small molecule PTC596 and proteasome inhibitors suppresses the growth of myeloma cells.

The novel small molecule PTC596 inhibits microtubule polymerization and its clinical development has been initiated for some solid cancers. We herein investigated the preclinical efficacy of PTC596 alone and in combination with proteasome inhibitors in the treatment of multiple myeloma (MM). PTC596 inhibited the proliferation of MM cell lines as well as primary MM samples in vitro, and this was confirmed with MM cell lines in vivo. PTC596 synergized with bortezomib or carfilzomib to inhibit the growth of MM cells in vitro. The combination treatment of PTC596 with bortezomib exerted synergistic effects in a xenograft model of human MM cell lines in immunodeficient mice and exhibited acceptable tolerability. Mechanistically, treatment with PTC596 induced cell cycle arrest at G2/M phase followed by apoptotic cell death, associated with the inhibition of microtubule polymerization. RNA sequence analysis also revealed that PTC596 and the combination with bortezomib affected the cell cycle and apoptosis in MM cells. Importantly, endoplasmic reticulum stress induced by bortezomib was enhanced by PTC596, providing an underlying mechanism of action of the combination therapy. Our results indicate that PTC596 alone and in combination with proteasome inhibition are potential novel therapeutic options to improve outcomes in patients with MM.

Epigenetic Mechanisms of Therapy Resistance in Diffuse Large B Cell Lymphoma (DLBCL).

Diffuse large B cell lymphoma (DLBCL) is the most common histological subtype of non-Hodgkin B cell lymphoma (NHL), and manifests highly heterogeneous genetic/phenotypic characteristics as well as variable responses to conventional immunochemotherapy. Genetic profiling of DLBCL patients has revealed highly recurrent mutations of epigenetic regulator genes such as CREBBP, KMT2D, EZH2 and TET2. These mutations drive malignant transformation through aberrant epigenetic programming of B-cells and may influence clinical outcomes. These and other chromatin modifier genes also play critical roles in normal B-cells, as they undergo the various phenotypic transitions characteristic of the humoral immune response. Many of these functions have to do with impairing immune surveillance and may critically mediate resistance to immunotherapies. In this review, we describe how epigenetic dysfunction induces lymphomagenesis and discuss ways of implementing precision epigenetic therapies to reverse these immune resistant phenotypes.

Epigenetic, Metabolic, and Immune Crosstalk in Germinal-Center-Derived B-Cell Lymphomas: Unveiling New Vulnerabilities for Rational Combination Therapies.

B-cell non-Hodgkin lymphomas (B-NHLs) are highly heterogenous by genetic, phenotypic, and clinical appearance. Next-generation sequencing technologies and multi-dimensional data analyses have further refined the way these diseases can be more precisely classified by specific genomic, epigenomic, and transcriptomic characteristics. The molecular and genetic heterogeneity of B-NHLs may contribute to the poor outcome of some of these diseases, suggesting that more personalized precision-medicine approaches are needed for improved therapeutic efficacy. The germinal center (GC) B-cell like diffuse large B-cell lymphomas (GCB-DLBCLs) and follicular lymphomas (FLs) share specific epigenetic programs. These diseases often remain difficult to treat and surprisingly do not respond advanced immunotherapies, despite arising in secondary lymphoid organs at sites of antigen recognition. Epigenetic dysregulation is a hallmark of GCB-DLBCLs and FLs, with gain-of-function (GOF) mutations in the histone methyltransferase EZH2, loss-of-function (LOF) mutations in histone acetyl transferases CREBBP and EP300, and the histone methyltransferase KMT2D representing the most prevalent genetic lesions driving these diseases. These mutations have the common effect to disrupt the interactions between lymphoma cells and the immune microenvironment, via decreased antigen presentation and responsiveness to IFN-γ and CD40 signaling pathways. This indicates that immune evasion is a key step in GC B-cell lymphomagenesis. EZH2 inhibitors are now approved for the treatment of FL and selective HDAC3 inhibitors counteracting the effects of CREBBP LOF mutations are under development. These treatments can help restore the immune control of GCB lymphomas, and may represent optimal candidate agents for more effective combination with immunotherapies. Here, we review recent progress in understanding the impact of mutant chromatin modifiers on immune evasion in GCB lymphomas. We provide new insights on how the epigenetic program of these diseases may be regulated at the level of metabolism, discussing the role of metabolic intermediates as cofactors of epigenetic enzymes. In addition, lymphoma metabolic adaptation can negatively influence the immune microenvironment, further contributing to the development of immune cold tumors, poorly infiltrated by effector immune cells. Based on these findings, we discuss relevant candidate epigenetic/metabolic/immune targets for rational combination therapies to investigate as more effective precision-medicine approaches for GCB lymphomas.

Akt inhibition synergizes with polycomb repressive complex 2 inhibition in the treatment of multiple myeloma.

Polycomb repressive complex 2 (PRC2) components, EZH2 and its homolog EZH1, and PI3K/Akt signaling pathway are focal points as therapeutic targets for multiple myeloma. However, the exact crosstalk between their downstream targets remains unclear. We herein elucidated some epigenetic interactions following Akt inhibition and demonstrated the efficacy of the combined inhibition of Akt and PRC2. We found that TAS-117, a potent and selective Akt inhibitor, downregulated EZH2 expression at the mRNA and protein levels via interference with the Rb-E2F pathway, while EZH1 was compensatively upregulated to maintain H3K27me3 modifications. Consistent with these results, the dual EZH2/EZH1 inhibitor, UNC1999, but not the selective EZH2 inhibitor, GSK126, synergistically enhanced TAS-117-induced cytotoxicity and provoked myeloma cell apoptosis. RNA-seq analysis revealed the activation of the FOXO signaling pathway after TAS-117 treatment. FOXO3/4 mRNA and their downstream targets were upregulated with the enhanced nuclear localization of FOXO3 protein after TAS-117 treatment. ChIP assays confirmed the direct binding of FOXO3 to EZH1 promoter, which was enhanced by TAS-117 treatment. Moreover, FOXO3 knockdown repressed EZH1 expression. Collectively, the present results reveal some molecular interactions between Akt signaling and epigenetic modulators, which emphasize the benefits of targeting PRC2 full activity and the Akt pathway as a therapeutic option for multiple myeloma.

KDM2B in polycomb repressive complex 1.1 functions as a tumor suppressor in the initiation of T-cell leukemogenesis.

KDM2B together with RING1B, PCGF1, and BCOR or BCORL1 comprise polycomb repressive complex 1.1 (PRC1.1), a noncanonical PRC1 that catalyzes H2AK119ub1. It binds to nonmethylated CpG islands through its zinc finger-CxxC DNA binding domain and recruits the complex to target gene loci. Recent studies identified the loss of function mutations in the PRC1.1 gene, BCOR and BCORL1 in human T-cell acute lymphoblastic leukemia (T-ALL). We previously reported that Bcor insufficiency induces T-ALL in mice, supporting a tumor suppressor role for BCOR. However, the function of BCOR responsible for tumor suppression, either its corepressor function for BCL6 or that as a component of PRC1.1, remains unclear. We herein examined mice specifically lacking the zinc finger-CxxC domain of KDM2B in hematopoietic cells. Similar to Bcor-deficient mice, Kdm2b-deficient mice developed lethal T-ALL mostly in a NOTCH1-dependent manner. A chromatin immunoprecipitation sequence analysis of thymocytes revealed the binding of KDM2B at promoter regions, at which BCOR and EZH2 colocalized. KDM2B target genes markedly overlapped with those of NOTCH1 in human T-ALL cells, suggesting that noncanonical PRC1.1 antagonizes NOTCH1-mediated gene activation. KDM2B target genes were expressed at higher levels than the others and were marked with high levels of H2AK119ub1 and H3K4me3, but low levels of H3K27me3, suggesting that KDM2B target genes are transcriptionally active or primed for activation. These results indicate that PRC1.1 plays a key role in restricting excessive transcriptional activation by active NOTCH1, thereby acting as a tumor suppressor in the initiation of T-cell leukemogenesis.

Bmi1 restricts the adipogenic differentiation of bone marrow stromal cells to maintain the integrity of the hematopoietic stem cell niche.

The polycomb group protein Bmi1 maintains hematopoietic stem cell (HSC) functions. We previously reported that Bmi1-deficient mice exhibited progressive fatty changes in bone marrow (BM). A large portion of HSCs reside in the perivascular niche created partly by endothelial cells and leptin receptor+ (LepR+) BM stromal cells. To clarify how Bmi1 regulates the HSC niche, we specifically deleted Bmi1 in LepR+ cells in mice. The Bmi1 deletion promoted the adipogenic differentiation of LepR+ stromal cells and caused progressive fatty changes in the BM of limb bones with age, resulting in reductions in the numbers of HSCs and progenitors in BM and enhanced extramedullary hematopoiesis. This adipogenic change was also evident during BM regeneration after irradiation. Several adipogenic regulator genes appeared to be regulated by Bmi1. Our results indicate that Bmi1 keeps the adipogenic differentiation program repressed in BM stromal cells to maintain the integrity of the HSC niche.

Immunomodulator-associated Epstein-Barr virus-positive mucocutaneous ulcer in a patient with refractory Crohn's disease.

Epstein-Barr virus (EBV)-positive mucocutaneous ulcer is a B-cell lymphoproliferative disorder occurring in elderly or iatrogenic immunocompromised patients. We report a 27-year-old male patient with Crohn's disease (CD) who developed immunomodulator-associated lymphoproliferative disorder. The patient was diagnosed with CD at the age of 17 and was treated with maintenance therapy including high-dose infliximab and azathioprine. When he was admitted to our hospital with a diagnosis of intestinal obstruction, his abdominal computed tomography findings showed not only colonic wall thickening and narrowing of the descending colon but also multiple liver tumor lesions. His ileus symptom improved with conservative therapy, and a pathological evaluation of the tissue biopsy specimens from the descending colon and liver lesions indicated a morphological diagnosis of EBV-positive diffuse large B-cell lymphoma. This was a case of iatrogenic immunodeficiency-associated lymphoproliferative disorder due to an immunomodulator. The treatment was initiated with chemotherapy, but he died of disease progression 10 months after the diagnosis of lymphoma. Although cases of lymphoproliferative disorder due to treatment modalities used for CD are rare in Japan, an increase in the risk of lymphoproliferative diseases should be considered in patients with CD treated with immunomodulatory agents.

Low incidence of thromboembolism in multiple myeloma patients receiving immunomodulatory drugs; a retrospective single-institution analysis.

Anti-platelet agents or anticoagulants are administered for patients with multiple myeloma (MM) receiving immunomodulatory drugs (IMiDs) to prevent thrombotic events (TEs). However, there is a discrepancy between current guidelines and clinical practice in thromboprophylaxis and the varied incidence of TEs depending on patient cohort. Therefore, a consensus on the optimal thromboprophylactic strategy is needed. To determine an appropriate strategy for the prevention of TEs in MM patients receiving IMiDs, we performed a retrospective single-institution analysis. In total, 95 MM patients (62% male, median age 65 years, range 30-85 years) from November 2008 to January 2018 were recruited, and 140 cases were analyzed in the medical-record-based study. Thromboprophylactic drugs were given to 69% of patients, anti-platelet agents to 66%, and anticoagulants to 3.0%. Seven TEs (5.0%) and six bleeding events (4.3%) were observed, but no patients died from thrombohemorrhage. The median follow-up period was 184 days (range 21-2224), and the cumulative TE incidence was 1.7% at 3 months, 7.0% at 1 year, and 12.5% at 3 years. Multivariate analysis determined that age > 70 years (p = 0.012) and BMI < 18.5 kg/m2 (p = 0.042) were the significant risk factors of TE. A low incidence of TEs was observed despite the low adherence to guideline recommendations for anticoagulant administration. These results suggest that anti-platelet agents are sufficient for thromboprophylaxis. A high-risk group of TEs in MM patients receiving IMiDs was identified, and a larger study is needed to confirm these findings.

Genetic and transcriptional landscape of plasma cells in POEMS syndrome.

POEMS syndrome is a rare paraneoplastic disease associated with monoclonal plasma cells; however, the pathogenic importance of plasma cells remains unclear. We performed comprehensive genetic analyses of plasma cells in 20 patients with POEMS syndrome. Whole exome sequencing was performed in 11 cases and found a total of 308 somatic mutations in 285 genes. Targeted sequencing was performed in all 20 cases and identified 20 mutations in 7 recurrently mutated genes, namely KLHL6, LTB, EHD1, EML4, HEPHL1, HIPK1, and PCDH10. None of the driver gene mutations frequently found in multiple myeloma (MM) such as NRAS, KRAS, BRAF, and TP53 was detected. Copy number analysis showed chromosomal abnormalities shared with monoclonal gammopathy of undetermined significance (MGUS), suggesting a partial overlap in the early development of MGUS and POEMS syndrome. RNA sequencing revealed a transcription profile specific to POEMS syndrome when compared with normal plasma cells, MGUS and MM. Unexpectedly, disease-specific VEGFA expression was not increased in POEMS syndrome. Our study illustrates that the genetic and transcriptional profiles of plasma cells in POEMS syndrome are distinct from MM and MGUS, indicating unique function of clonal plasma cells in its pathogenesis.

Multiple cystic lung lesions and autoimmune thrombocytopaenia developing after chemotherapy for pulmonary indolent B-cell lymphoma with plasmacytic differentiation.

Among lung malignancies, primary pulmonary lymphoma is rare and many of them are indolent B-cell lymphomas. We describe a case of primary pulmonary indolent B-cell lymphoma with plasmacytic differentiation, which exacerbated with the manifestation of macroglobulinaemia and was successfully treated using chemotherapy. The patient subsequently developed pulmonary cysts and thrombocytopaenia due to autoimmune pathology and was successfully treated using prednisolone. This case suggests that in indolent B-cell lymphoma with plasmacytic differentiation, immunoglobulin M level should be carefully followed even if it is within the normal range at lymphoma onset. Additionally, new cystic pulmonary infiltrates that develop during the post-treatment follow-up of an indolent pulmonary B-cell lymphoma may indicate pulmonary lymphoma recurrence, but there is also a possibility of an immunological complication.